QSC Audio CX168 User manual

Brand: QSC Audio

Model: CX168

Category: Audio amplifiers

Type: User manual

User Manual

CX168

8-Channel Installed Sound

Professional Audio Amplifier

TD-000095-00 rev.A

*TD-000095-00*

CAUTION: TO REDUCE THE RISK OF ELECTRIC SHOCK, DO

NOT REMOVE THE COVER. NO USER-SERVICEABLE PARTS

INSIDE. REFER SERVICING TO QUALIFIED PERSONNEL.

FCC INTERFERENCE STATEMENT

NOTE: This equipment has been tested and found to comply with the limits for a class B digital device, pursuant to part

15 of the FCC rules. These limits are designed to provide reasonable protection against harmful interference in a

residential installation. This equipment generates, uses, and can radiate radio frequency energy and if not installed

and used in accordance to the instructions, may cause harmful interference to radio communications. However, there is

no guarantee that interference will not occur in a particular installation. If this equipment does cause harmful

interference to radio or television reception, which can be determined by switching the equipment off and on, the user

is encouraged to try to correct the interference by one or more of the following measures:

- Reorient or relocate the receiving antenna.

- Increase the separation between the equipment and the receiver.

- Connect the equipment into an outlet on a circuit different from that to which the receiver is connected.

- Consult the dealer or an experienced radio or TV technician for help.

CAUTION

RISK OF ELECTRIC SHOCK

DO NOT OPEN

QSC® is a registered trademark of QSC Audio Products, Inc.

“QSC” and the QSC logo are registered with the U.S. Patent and Trademark Office

The Audio Precision logo is the property of Audio Precision, Beaverton OR

All trademarks are the property of their respective owners.

IMPORTANT SAFETY PRECAUTIONS

& EXPLANATION OF SYMBOLS

WARNING: TO PREVENT FIRE OR ELECTRIC SHOCK, DO NOT EXPOSE THIS

EQUIPMENT TO RAIN OR MOISTURE.

The lightning flash with arrowhead symbol within an equilateral triangle is intended to alert the user to the

presence of uninsulated “dangerous” voltage within the product’s enclosure that may be of sufficient

magnitude to constitute a risk of electric shock to humans.

The exclamation point within an equilateral triangle is intended to alert the user to the

presence of important operating and maintenance (servicing) instructions in this manual.

This amplifier has a serial number located on the rear panel.

Please write this and the model number down and keep them for your records.

Model: CX168

Serial Number:______________________________

Date of Purchase:____________________________

Purchased From:_____________________________

The lightning flashes printed next to the OUTPUT terminals of all ISA amplifiers are intended to alert the user

to the risk of hazardous energy. Output connectors that could pose a risk are marked with the lightning flash.

Do not touch output terminals while amplifier power is on. Make all connections with amplifier turned off.

INTRODUCTION:

CX168 Overview .......................................................................................4

Front Panel Illustration .........................................................................................4

Rear Panel Illustration ........................................................................................5

Mounting Dimensions .........................................................................5

INSTALLATION:

What is Included..............................................................................................6

Rack Mounting ....................................................................................6

Supporting the Rear of the Amplifier.....................................................6

Fan Cooling...........................................................................................7

AC Mains (AC Power) Connection..............................................................................7

SETUP:

Setting the Configuration (MODE) Switches....................................................8

Setting Operating Mode (Stereo, Parallel, or Bridge)........................................9

Clip Limiter Setting.............................................................................10

Low Frequency (Subaudio) Filter Settings................................................................10

Low Frequency Filtering Tips and CX168 Frequency Response Curve...................11

CONNECTIONS:

Inputs: Connecting to the Input Terminal Block Inputs ...................................12

Connecting to the DataPort Inputs.......................................................13

Outputs: Connecting the Outputs in Stereo or in Bridge Mode .........................14

How to use the 8-pin Output Connectors................................15

OPERATION:

Power Switch ............................................................................................16

LED Indicators .......................................................................................17

Gain Controls ......................................................................................18

Security Plate for Gain Controls .........................................................19

DataPort Connector ...................................................................................20

DataPort Guidelines for the CX168.........................................21

APPLICATIONS:

Four Room, Stereo Feed..............................................................................................22

Tri-Amplified, Stereo Cabinets with Subwoofer..............................................22

APPENDIX:

Detailed Explanation of Stereo, Parallel, and Bridge Operating Modes..........24

Multiple Speaker Loads in Series........................................................26

Multiple Speaker Loads in Parallel........................................................27

TROUBLESHOOTING ........................................................................................................28

SPECIFICATIONS ......................................................................................................30

WARRANTY INFORMATION .............................................................................................32

HOW TO CONTACT QSC AUDIO PRODUCTS ............................................................................32

TABLE OF CONTENTS

FRONT PANEL WITH

SECURITY PLATE

INTRODUCTION

Congratulations on your purchase of the CX168 power

amplifier. To help you obtain the best results from your

purchase, we encourage you to carefully review this manual.

With information including connections, configuration and

operation, it offers many useful guidelines.

The CX168 provides a high level of channel density in a small,

lightweight form factor ideal for multi-zone audio systems.

Representing the culmination of QSC’s extensive experience

in power amplifier development, the CX168 is a highly

versatile, reliable, and user-friendly tool that will likely remain

a central component of your system for years to come.

Like the entire CX Series, the CX168 is equipped with QSC’s

exclusive PowerWave

switching power supply technology

to virtually eliminate noise and hum while reducing the unit’s

overall weight. Comprehensive protection circuitry includes

DC, infrasonic, thermal overload and short circuit protection.

The CX168 includes 4 HD15 DataPorts (one per channel pair)

for remote management or DSP. These ports allow each

channel pair to be governed by QSControl, QSC’s audio

networking system—enabling the system operator to control

amplifier gain levels, check the unit’s clipping and thermal

status, plus monitor numerous additional system parameters.

Alternatively, these DataPorts facilitate connection of signal

processing equipment, such as QSC’s DSP-3, which offers two

channels of independent digital signal processing - including

crossover filters, shelf filters, signal delay, compression, peak

limiting, and parametric filters.

As individual channel pairs may be bridged, the CX168 is

configurable as a 4-, 5-, 6-, 7-, or 8-channel unit. Further, the

CX168 features detachable Phoenix-style input and output

connectors—enabling the audio system to be wired with

greater ease. Other features include 1-dB recessed and

detented gain controls and a security cover for tamper-proof

installations.

The CX168 is easy to use. All operating mode switches are

grouped together on the rear panel, with one switchblock per

channel pair. These switches enable clip limiter on/off, LF

filter on/off, LF filter select and operation modes. The

amplifier’s front panel includes corresponding LEDs to indicate

Bridged or Parallel modes in addition to Signal and Clip

status.

Your CX168 power amplifier was designed to provide many

years of trouble-free, great-sounding operation. We hope you

enjoy your new CX168.

FRONT PANEL

INTRODUCTION

REAR PANEL

DIMENSIONS

AND MOUNTING

POINTS

INSTALLATION: UNPACKING & RACK MOUNTING

Rack Mounting

Supporting the Rear of the Amplifier

What is Included

Unless the amplifier is being installed in its final, fixed

location, we strongly recommend supporting the rear of the

amplifier.

Supporting the rear of the amplifier is required for mobile

and portable use. If the amplifier is to be transported in any

way, install the optional rear rack mounting ear kit to

support the rear of the amplifier. During transport, the shock

loads encountered on the chassis and rack can easily

damage an unsupported amplifier and the rack rails. With

proper support, reliability is enhanced.

Rear rack mounting ear kits are an accessory item and are

available from QSC’s Technical Services Department or from

your dealer or distributor. Refer to the literature included

with the rack mounting ear kit for installation instructions.

Two methods of rear rack mounting ear attachment are

possible; use the method that best suits you application.

Use four screws and washers to secure the amplifier to the

equipment rack rails. Support the weight of the amplifier

while securing it to the rails to avoid bending or distorting

the mounting ears. The amplifier may be used in an

equipment rack or as a stand-alone unit. Rack mounting is

optional. Self-adhesive rubber feet are provided for non-rack

mount applications.

Save the container and packing material

so the amplifier may be shipped without

damage if service is ever required. If the

original container is not available, be

sure to use a strong shipping container with enough

packing material to prevent the amplifier from being

damaged in transit.

Optional rear rack mounting ear attachment methods-

refer to the rear rack mounting ear kit’s documentation

for details

Your CX168 shipping container, as shipped from the factory,

includes:

- CX168 eight channel audio power amplifier

- this user’s manual

- security cover (plate) for gain controls

- self-adhesive rubber feet (use for non-rack mount applications)

- eight 3-pin terminal block input connectors

- two 8-pin terminal block output connectors

- #14AWG IEC-type detachable power cord

INSTALLATION: COOLING & AC MAINS REQUIREMENTS

AC Mains Connection

Do not obstruct the front or rear air vents! Make sure that plenty of cool air can enter

the rack, especially if there are other units which exhaust hot air into it.

Connecting to the wrong line voltage is

dangerous and may damage the amplifier or

constitute the risk of electric shock. Verify the

correct AC line voltage by checking the

specification printed on the serial number

label on the rear panel.

Air flow in QSC amplifiers

The CX168 amplifier draws cool air into the rear of the

amplifier and exhausts hot air from the front. This is done so

the equipment in the rack stays as cool as possible. This

method of cooling gives the operator “direct” air tempera-

ture feedback at the front of the rack, where it is the most

convenient. The front panel’s temperature indicates “how

hard” the amplifier is working.

The fan varies speed automatically to maintain safe internal

temperatures and minimize noise. Keep the front and rear

vents clear to allow full air flow.

The correct AC line voltage is shown on the

serial number label.

Fan Cooling

The correct AC line voltage is shown on

the serial number label. Make sure the AC

mains is the correct voltage. Connecting to the

wrong line voltage is dangerous and may

damage the amplifier.

Connect the AC line cord by orienting the

IEC plug correctly and pushing the plug firmly

into the IEC receptacle. It should seat tightly. It

can only be inserted when it is properly

oriented.

Use the cord supplied with the amplifier, or an

equivalent. Insure that the wire gauge of the

cord is #14AWG. Use of #16 or #18 AWG can

be dangerous and is not recommended.

Use the best possible connection to the

AC power source. Avoid extension cords as

they will cause some voltage drop between

the AC source and you amplifier. If the use of

an extension cord is required, ensure that it is

the shortest length possible and is at least

#14 AWG. Ensure that all grounding connec-

tions are maintained.

NOTE: Excessive length or inadequate gauge

may result in short muting episodes if all

channels are driven to full power.

SETUP: SETTING THE MODE CONFIGURATION DIP SWITCHES

Setup

By using the mode switches and connecting to the amplifier

properly, the CX168 amplifier can be configured as a 1 to 8

channel amplifier. This flexibility enables the CX168 to be

used for most any multichannel application.

The CX168 can be thought of as four separate 2-channel

amplifiers on one chassis. Each of the four amplifier

sections may be operated in Stereo, Parallel, or Bridge mode

independently of the others. For example, channels 1 & 2

could be set for stereo operation while channels 3 & 4 are

set for parallel operation; all while channels 5 & 6 and

channels 7 & 8 are set for bridge mode.

The channels are grouped as follows:

Channels 1 and 2

Channels 3 and 4

Channels 5 and 6

Channels 7 and 8

You can set the operating mode for each group by setting

that group’s configuration DIP switches in the desired

positions. It is NOT POSSIBLE to group the channels

differently. For instance, you can not bridge channels 3 & 5

because they are not in the same channel group.

Before setting the configuration DIP switches, you must first

decide how the amplifier will connect to the speaker

system.

“MODE” configuration DIP switches are located on

the rear panel and look like the illustration above.

Switch positions shown are for example only. Set

switches as required for your application.

“MODE” switch settings and speaker connection diagrams are printed on a rear panel label, as shown, above.

SETUP: SETTING THE MODE: STEREO, PARALLEL, OR BRIDGE

Modes

Stereo- Stereo mode supports two completely

separate audio channels, usually referred to as ‘left’

and ‘right’. Stereo configurations have two separate

input signals and two separate output signals.

Parallel- Parallel mode applies one input signal to

both channels. Both inputs of a channel pair are

connected in parallel when the mode switch is set

for parallel, therefore, connect only one input per

channel pair when in parallel mode. The outputs are

connected the same as stereo mode. Each speaker

will be supplied the same signal, which is still

controlled by that channel’s gain control.

The following descriptions apply to a channel pair (such as Ch. 1 & 2 or Ch. 7 & 8). It is possible to set each channel pair’s mode

differently and customize the system configuration. All possible combinations will not be shown. The following describes the

behavior of one channel pair in the three modes of operation and the

BRDG

and

PAR

LED’s:

Bridge- Bridge mode combines the two channels of

a pair (such as Ch. 3 & Ch. 4) into one higher-

powered channel. Like parallel mode, both inputs of

a channel pair are connected in parallel when the

mode switch is set for parallel, therefore, connect

only one input per channel pair when in bridge

mode. There are 4 possible channel pairs that can

be bridged on the CX168. They are Ch.1-2 Bridge,

Ch. 3-4 Bridge, Ch. 5-6 Bridge, and Ch. 7-8 Bridge.

Any pair or number of pairs can be independently

configured in bridge mode. Use the first channel’s

input and gain control when in bridge mode. The

second channel’s gain control is non-operative and

should be turned all the way down.

For pictorial description of operating modes, see Appendix.

Mode switch settings and LED indication for parallel mode operation.

BRDG indicator and PAR indicator should be illuminated when in bridge

mode.

Mode switch settings and LED indication for stereo mode operation.

BRDG and PAR indicators should not be illuminated when in stereo mode.

Mode switch settings and LED indication for parallel mode operation.

PAR indicator should be illuminated and BRDG indicator should not be

illuminated when in parallel mode.

Note! Do not connect more than one input per channel pair when operating in parallel or bridge mode. However,

in parallel or bridge mode, the unused input terminals may be used for daisy-chaining the input signal to other

channels of the CX168 or to other amplifiers.

SETUP: MODE SWITCHES: CLIP LIMITER AND LOW FREQUENCY FILTERS

The CX168 amplifier has separate clip limiters for each of

the 8 channels. These clip limiters respond only to actual

amplifier clipping. Amplifier clipping generates internal error

signals which cause the clip limiter to quickly reduce gain

and minimize the overdrive. To preserve as much of the

program dynamics as possible, limiting occurs only during

actual clipping. Each channel’s clip limiter can be switched

on or off individually.

CAUTION! Clip limiting reduces extreme

overdrive peaks, allowing a higher average

signal level without distortion. Increasing the

gain with the clip limiter engaged until

clipping is again audible, can double the

average output power. Be careful not to

exceed the power rating of the speakers!

Clip Limiter

The clip limiter is internally set to respond as fast as

possible after clipping is detected. For program material that

is primarily “full-range”, the effect on the overall audio

quality should be imperceptible. We recommend using the

clip limiters for almost all applications, especially full-range

audio applications. Clipping can cause high-frequency

artifacts to be output to the speakers, potentially damaging

fragile high-frequency drivers.

For program material that is primarily low-frequency in

nature (low-frequency or subwoofer drive) this may be

perceived as a “rubbery” effect on the audio. If this is the

case, it may be preferable to turn the clip limiters off and let

the amplifier clip occasionally. With robust, low-frequency

drivers, the occasional clipping should cause no problems.

Low Frequency Filter

When driving speakers with limited low frequency

response, it is important to limit the low frequency

response of the amplifier. Doing so can result in more

usable bass response since the speaker is not being

overloaded by very low frequencies it can’t handle.

Explanation-

Low frequency sound waves require much

more speaker cone motion to produce the same apparent

loudness as higher frequencies. Properly designed speaker

enclosures help the speaker to move more air with less

motion using techniques like porting. Such enclosures only

benefit from porting down to a certain frequency. Below

this frequency, the speaker is “unloaded” and is basically

free to move around uncontrollably without producing much

bass. Limiting the frequency range of the low frequency

content enables the speaker to behave the way it was

designed to. If frequencies lower than designed are

supplied to the speaker, performance will degrade.

All low frequency filters will change the character of low

frequency transients. For best results, the cabinet design,

speaker capabilities, and program material must be taken

into account when configuring low frequency filtering.

SETUP: MODE SWITCHES: CLIP LIMITER AND LOW FREQUENCY FILTERS

Frequency Response Curves

Filter off

Filter ON, 33 Hz.

Filter ON, 70 Hz.

Low Frequency Filtering Tips:

 The OFF position should be used only for subwoofer systems with rated frequency response below 33 Hz. or if low frequency

filtering is provided by other devices.

 Know the specification of the speaker cabinet you are driving. Match the low frequency roll off setting to the specified low

frequency capability of the speaker cabinet. Do not drive the speaker with frequencies below its rating.

 Unless you have low frequency filtering before the amplifier, use the low frequency filter to protect your loudspeakers from

cone over-excursion caused by frequencies below the speaker’s limits.

 The 33 Hz. rolloff is a good “all purpose” setting. Turn the filter on by setting the appropriate DIP switch to ON position and

select 33 Hz. using its 33/70 Hz. DIP switch. This setting is a good starting point for most large, full-range cabinets.

 The 70 Hz. rolloff is a good setting to use with smaller, compact speaker cabinets having limited bass capability. Turn the

filter ON and select the 70 Hz. setting when using smaller cabinets.

 The frequency selection ( 33 or 70 Hertz) has no effect unless the filter is set to the ON position.

Unbalanced inputs: Connect the

conductors to the connector as

shown. Make sure that the unused

side of the balanced input is

connected to ground, as shown.

Terminal block: unbalanced connections

Terminal block: balanced connections

CONNECTIONS: INPUTS- Using the Terminal Block Inputs

jumper

shield

Terminal Block Connectors:

Each channel has an active balanced "Euro-style" terminal block

input jack. These terminal blocks allow the input wiring to be

terminated using simple hand tools and allows for quick

reconfiguration when needed. The input impedance is 20k ohm

balanced or 10k ohm unbalanced.

Balanced connection is recommended for all audio inputs.

Balanced signals are less prone to AC hum and other electrical

noise. Unbalanced signals can be suitable for short cable runs.

The signal source's output impedance should be less than 600

ohms to avoid high frequency loss in long cables.

If the DataPort is being used for the input signal source,

the terminal block connections should not be used for

inputs.

However, they may be used for daisy chaining the

DataPort input signal to other channels or amplifiers. The signal

available from the terminal block input connections will be about

10 dB lower than the signal presented to the DataPort.

shield

TERMINAL BLOCK

CONNECTORS

Balanced inputs: Connect the

conductors to the connector as

shown.

CONNECTIONS: INPUTS- Using the DataPorts

If used, the DataPort must be connected to a QSC DataPort product

using a QSC DataPort cable. Do not use computer cables; they look

similar but can cause operational problems with your amplifier and/or

DataPort accessories.

The CX168 amplifier is equipped with four QSC DataPort connections

that may be used for connecting to accessory QSC DataPort devices.

Each DataPort services a specific channel pair; the channels are paired

as:

Ch. 1 and Ch. 2

Ch. 3 and Ch. 4

Ch. 5 and Ch. 6

Ch. 7 and Ch. 8

Each DataPort and its associated terminal block input pair can be

configured independently (there is no requirement to use a DataPort

connection for all channels). Only the Ch.1-Ch.2 DataPort can control the

power supply standby mode.

The DataPort connection will supply the input signals to the amplifier. If

using the DataPort connection for audio input signals, do not apply

inputs to the terminal block input connectors. If the DataPort connection

is used only for monitoring amplifier operating conditions and NOT for

providing audio inputs to the amplifier, then the terminal block inputs

may be used to supply the audio inputs to the amplifier.

How to Connect to the DataPort:

Basic DataPort Notes:

1- The amplifier Gain controls will need to be set at their anticipated high-level setting. Use reduced level

setting during setup & test.

2- If using the DataPort for audio input signals, control of the audio level will be accomplished with the

DataPort accessory device to which the amp is connected.

3- Control of the amplifier’s AC power standby mode will only be possible via the Ch.1-2 DataPort. The

amplifier’s POWER switch must be physically set to the “ON” position to use the standby control feature.

4- The order in which the four DataPorts are connected to external devices makes no difference to the

amplifier. However, the host controller to which the amplifier is connected will show the channels in the

order that cables are connected.

Direct mounting of DataPort accessories is NOT supported by the CX168 amplifier. Devices

that are normally mounted directly to the amplifier must be mounted remotely and connected to the

DataPort using a DataPort cable. This is due to the high density of connectors on an eight-channel

amplifier; there is not enough space to allow for accessories to be mounted directly to the back of the

amplifier.

If the accessory attaches with a QSC DataPort cable, orient the HD-15 male plug correctly with

the DataPort socket on the amplifier (it is “D” shaped and will fit only one way). Push the plug onto the

socket firmly and ensure it is seated properly. Finger-tighten the 2 retaining screws. Do not over tighten.

DATAPORT

CONNECTORS

CONNECTIONS: OUTPUTS

BRIDGE MODE PRECAUTIONS:

Do not use 2 ohm or 4 ohm loads in bridge mode! 8

ohms is the minimum impedance for bridge mode

operation. This mode puts a high demand on the

amplifier and speaker. Excessive clipping may cause

protective muting or speaker damage. Ensure the speaker has

a sufficient power rating.

Refer to the label on the rear panel of the amplifier for proper wiring connections. The output connection for STEREO and

PARALLEL modes is on the left side of the label , while the output connection for BRIDGE mode is shown to the right side of

the label. Note: Polarity changes from channel to channel and is different for bridge mode. Be certain of polarity of connec-

tions before applying power. Reversed polarity may degrade audio frequency response.

Speaker connection diagrams and “MODE” switch settings are printed on a rear panel label, as shown, above.

Outputs

Stereo and Parallel Mode

Bridge Mode

In bridge mode, each speaker is connected to a bridged-pair of

outputs. The channels must first be “bridged” by setting the

mode configuration switches to the bridge settings. Then con-

nect the speakers as shown on the right side of the connection

diagram (rear panel) or in the diagram, right.

Use 8 ohm minimum impedance in bridged mode.

Ensure the mode configuration switches are set for bridge

mode when connecting speakers to bridged output pairs .

In stereo or parallel mode, each speaker is connected to its

own individual channel of the amplifier. This connection

method is shown on the left side of the connection diagram

(rear panel) or in the diagram, right.

Use 4 ohm minimum impedance in stereo or parallel

mode. Ensure the mode configuration switches are set for

stereo or parallel mode when connecting speakers to each

channel’s output.

Bridge connection- single speaker shown connected to am-

plifier channels 5 and 6 (bridged with mode switch settings).

Ensure that all speaker connections maintain proper polar-

ity ( + to +, - to - ).

Stereo or parallel connection- single speaker shown con-

nected to amplifier channel 6 output. Ensure that all speaker

connections maintain proper polarity ( + to +, - to - ).

CONNECTIONS: OUTPUTS- USING THE TERMINAL BLOCK CONNECTORS

The output connections are made by attaching speaker

wires to the 8-pin terminal block connectors. Once these

connectors have been “populated” with the necessary

speaker wire connections, plug the terminal blocks into

their respective output jack.

The output jacks are configured in two discrete connectors.

One connector carries the connections for channels 1

through 4. The other, channels 5 through 8. Each connector

has 8 pins, each of which connects to the speaker wire

using a screw-clamp. Refer to the diagram, right, for the

basic connection procedure. Be sure that speaker polarity is

maintained. The locations of the “+” and “-” terminals on

the amplifier is not the same for each channel.

Ensure that all wires are neatly terminated with no loose

strands. Do not strip the insulation back excessively. Loose

strands and exposed wire beyond the terminals may cause

a short circuit and cause protective muting of the amplifier.

Once all the required connections have been made to the

terminal block connectors, they may be inserted into the

OUTPUTS jack on the rear panel. Orient the connector

properly (it only fits one way) and push it in until it is fully

seated in the receptacle. Note each connector is oriented so

its wires face outwards.

OUTPUT TERMINAL SAFETY WARNING!

Do not touch output terminals while amplifier power is on.

Make all connections with amplifier turned off. Risk of

hazardous energy!

How to make connections to the terminal block:

1- Strip the wires approximately 0.28” (7mm).

2- Twist any loose strands of wire together.

3- Loosen the appropriate retaining screw fully.

4- Insert the stripped wire into the receptacle.

5- Tighten the appropriate retaining screw to secure.

When selecting speaker cable (wire), always use the

largest wire size and shortest length of wire practical for

an installation. Larger wire sizes and shorter lengths

minimize power loss and degradation of damping factor. Do

not place speaker cables next to input wiring.

Terminal Block Connections

If the POWER LED fails to illuminate when

the switch is in the ON position:

The power switch is a rocker-type switch. It is located on

the left side of the front panel. To turn the amplifier on, push

in on the top of the switch. To turn the amplifier off, push in

on the bottom of the switch.

The green power LED should light up when the switch is in

the on position.

When the power is switched off, the LED may takes several

seconds to go out; this is normal.

OPERATION: POWER SWITCH and GAIN CONTROLS

1- Check the AC cord and insure that both ends are fully

inserted into their receptacles. If the power LED still fails to

illuminate,

2- Check the AC outlet for voltage with a circuit tester or

known good device (lamp, etc.).

3- Make sure that the amplifier is not in STANDBY mode. If

the amplifier is being controlled by one of its DataPort

connectors, the amplifier may be in standby mode. Verify the

AC power status from the DataPort device controlling the

amplifier.

Power Switch

The ‘POWER’ LED is located at the upper-left of

the gain controls section of the front panel. It is a

green LED that illuminates when the power is

turned on (and the amplifier is properly connected

to the correct AC source). The power LED extin-

guishes when the power is turned off.

To turn the amplifier ‘on’, push in on the top por-

tion of the rocker switch firmly. It should move

inward and snap into the ‘on’ position. After

switching on, the power LED should illuminate.

To turn the amplifier ‘off’, push in on the bottom

portion of the rocker switch firmly. It should move

inward and snap into the ‘off’ position. After

switching off, the power LED should extinguish.

OPERATION: LED INDICATORS

CLIP : Each channel has a red ‘clip’ LED that illumi-

nates when the channel clips. It is located to the upper-

right of each channel’s gain control.

Normal indication:

illuminates briefly at extreme

output power peaks. Occasional clipping at high power

levels may be normal. At power-on, the clip LEDs may

briefly flash during turn-on muting.

Continuous operation at high power may trigger the

thermal protection circuitry, shutting down the amplifier

and fully illuminating the clip LED. Operation will

resume after the amplifier has cooled down sufficiently.

SIGNAL: Each channel has a green ‘signal’ LED

located to the right of its gain control. The ‘signal’ LED

lights up when the input signal is sufficiently strong.

Normal indication:

illuminates when the input signal

is present and sufficiently strong.

POWER: The power ‘on’ indicator LED is located at the

upper-left of the gain control cluster. It is green and

illuminates when the power switch is set to the on

position and AC power is present at the IEC cord

receptacle.

Normal indication:

at power-on the LED will illumi-

nate.

If no indication:

check gain settings, input cables,

connections and audio source. If audio source is

extremely low signal strength, signal LED may not

illuminate; this is normal but indicates that the input

signal strength should be increased.

Occasional illumination:

normal for weak input

signal strength.

Fully illuminated (on):

normal.

If no indication:

Check AC power cord, AC mains, and

that the DataPort is not being used to force the

amplifier into ‘Standby’ mode.

When power is switched off:

the LED may take

several seconds to extinguish (go out); this is normal.

If no indication:

normal if the amplifier is operated at

nominal output levels. If the input signal is weak, it may

not be capable of driving the amplifier into clipping,

even at full gain.

Occasional illumination:

Occasional clipping (once

briefly every few seconds) when operation at high

power levels does not indicate trouble. Continuous

operation at high power may trigger the thermal

protection circuitry, shutting down the amplifier and

fully illuminating the clip LED.

Illuminated most of the time:

Not normal; for cleaner

sound, reduce the output of the amplifier and/or input

signal to avoid thermal shutdown of the amplifier and

possible speaker damage. If clipping persists at normal

levels, check for shorted or abnormal load impedances.

Fully illuminated (on):

Amplifier is in thermal shut

down. Reduce gain settings or input signal and allow

the amp to cool down. Leave the power on so that the

fan continues to run; operation will automatically

resume after the amplifier has cooled sufficiently.

LED Indicators

The LED indicators provide basic operation information to the operator. The ‘nor-

mal’ indications of the LED’s are shown, below. NOTE! The BRDG and PAR mode

indicator LED’s are discussed on page 9.

Gain Controls

Typical gain control showing attenuation level

markings and LED’s for the channel. Note that

there is only one BRDG (bridge) and one PAR

(parallel) indicator per channel pair.

Location of gain controls on the front panel of the CX168

Typical channel-pair control and indicator group on the CX168

OPERATION: GAIN CONTROLS

The gain controls are located on the right side of the front

panel. They are operated by rotating the control clockwise to

increase gain or counterclockwise to decrease gain. When

turned fully counterclockwise, gain is fully reduced and no

output signal will be present. When turned fully clockwise,

the voltage gain of the amplifier is +26dB and the output

signal will potentially be full strength (provided the input is

fully driven).

The gain controls are detented in 21 steps for repeatable

adjustment. Surrounding the Gain control, the power

attenuation level is shown in dB. Each detent is approxi-

mately 1dB change in amplifier gain.

To operate the gain control, rotate the control’s knob so that

the desired level is achieved. A small, flat-tipped screw-

driver (#1 blade size) is typically used. Be sure not to use

large screwdrivers as it is possible to damage the gain

control by applying excessive torque. Gain controls are

sensitive, electronic components and should be treated with

care.

Each channel pair’s gain controls and indicator LED’s are

grouped together as shown, right. The channels are paired

in the following manner:

Channel Pair #1- Ch. 1 and Ch. 2

Channel Pair #2- Ch. 3 and Ch. 4

Channel Pair #3- Ch. 5 and Ch. 6

Channel Pair #4- Ch. 7 and Ch. 8

As detailed in the ‘Setup’ section of this manual, channels

can only be paralleled and bridged within their channel pair.

Example- Channel 3 can be bridged with channel 4 only; it

can not be bridged with any other channel.

The dB markings around the gain controls are attenuation.

They show attenuation from full gain. At 0db attenuation,

the voltage gain of the amplifier is 26dB. If the gain control

is set at the 7dB attenuation position, then the voltage gain

of the amplifier is 19dB (26dB - 7 dB).

OPERATION: GAIN CONTROL SECURITY PLATE

Gain Control Security Plate

After final gain adjustments have been made, the gain controls can be covered with a security plate. This easy-to-use security plate

makes it difficult for others to adjust the gain. This may be desirable in instances where the gain controls should not be tampered with. To

install the security plate:

When properly installed, the security panel will still allow you

to monitor all the channel status LED’s and power LED. The

amplifier front panel will look like the illustration, right, after

installing the security plate.

4. Make sure the LED’s are visible, then tighten the

screw with the hex key. Do not over tighten!

3. Line up the tabs with the keyed portion of the

ventilation slots, insert into the slot and then slide

the panel fully right, locking it in the slot.

2. Orient the panel as shown and slide the right end

of the plate under the screw.

1. Use a 9/64” or 3.5mm hex key to loosen

the screw. Do not remove; just loosen sev-

eral turns.

QSC’s DataPort equipped amplifiers offer operators of larger

audio systems a high degree of system monitoring and

operation from remote locations. A system operator in a

sports complex might be located hundreds of yards (meters)

from the actual amplifiers, making ‘normal’ control and

monitoring of the system difficult, at best. By integrating

QSC’s DataPort-equipped amplifiers with QSC’s DataPort

accessories, a dependable and robust control and

monitoring solution can easily be implemented.

The DataPort is used for connection to optional QSC

DataPort accessories. DataPort accessory devices can

provide remote cinema monitoring, DSP, filter and crossover

functions.

The DataPort connections on the CX168 offer full-featured

implementation of DataPort accessories and supply the

required accessory voltage to DataPort devices that require

it. CX168 amplifiers DO NOT support direct mounting of

smaller accessories, like the DSP-3, due to the high density

of connectors on the rear panel but they may be connected

via cables.

Using the DataPort

OPERATION: USING THE QSC DATAPORT CONNECTIONS

DataPort Connectors

A single DataPort is assigned to each channel pair. Each DataPort

is marked with the channel numbers served by that DataPort. Note,

above, that each DataPort is clearly labeled and is located be-

tween its respective channel’s terminal block connectors.

Use a QSC DataPort cable to connect the CX168 DataPorts

to DataPort accessories. Consult the accessory’s

documentation for recommended mounting and interconnect

information.

Do not use terminal block connections for inputs when the

DataPort is used as the input signal source. If you do, the

signals from the DataPort and terminal block inputs will be

mixed, possibly with unexpected results.

See the following section for general operating notes

regarding the DataPorts on the CX168.

Connect to the DataPort using a QSC DataPort cable. Align the

connector with the socket housing and insert fully. Finger-tighten

the retaining screws.

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QSC Audio CX168 User manual

Brand: QSC Audio

Model: CX168

Category: Audio amplifiers

Type: User manual

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QSC Audio CX168 User manual

QSC Audio CX168 User manual

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